Chapter 8 Chemical Reactions

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2A chemical reaction is a process in which the physical and chemical properties of the original substances change as new substances with different physical and chemical properties are formed

3Law of Conservation of MassDuring a chemical or physical change, all mass remains the same.Mass is neither created nor destroyed.

4Parts of a chemical reactionSubscript tells the # of atoms in moleculeCoefficient tells # of molecules in reaction2 H2 + O H2Ocoefficientcoefficientsubscript

5Parts of a chemical equationReactant is what goes into a chemical reactionProduct is what results in the reaction2 H2 + O H2Oproductreactantreactant

6The ease with which atoms will form bonds is its bonding capacity.Capacity to reactThe ease with which atoms will form bonds is its bonding capacity.This capacity is directly related to the electrons and their placement and number within the energy levels.

7What happens when a chemical reaction occurs?Atoms can form moleculesMolecules can break apart to form atomsMolecules can react with other molecules

8Balancing Equations Start with the first atom on the reactants sideCount the total number of atoms of the element on left and then on the rightAdd a coefficient in front of atom(s) or compounds where necessaryNever change a subscriptGo back through each atom and recheck and/or change until # are equal on both sides of the equation

9Types of Chemical ReactionsSYNTHESIS2 or more substances combineDECOMPOSITIONcomplex substance breaks downSINGLE - REPLACEMENTuncombined element replaces another element in a compoundDOUBLE - REPLACEMENTatoms of 2 compounds replace each other (a flip-flop)

10synthesisSimple molecules or compounds combine to make a new and more complex substance2 H2 + O H2O

14In any chemical reaction: some energy is needed to start the change some energy is involved during the reaction

15ACTIVATION ENERGY is what is needed to get a reaction startedEx: striking a match

16Energy involved in the reaction can be either:Exothermic or Endothermic

17Exothermic ex means out therm means heatenergy is released during reactionthe energy in the reactants are higher than the productsEx: fireworks

18Endothermic endo means in therm means heatenergy is absorbed during reactionthe energy in the products are higher than the reactantsEx: chemical ice

19Kinetics is the study of reaction ratesIn order to react, atoms must collide.In order for bonds to be broken, formed or reformed, particles must collide at precisely the correct angle with the proper amount of energy.

20Four factors that influence the collision theory are . . .Rates of Chemical ReactionsThe more collisions, the faster the rate of the chemical reactionFour factors that influence the collision theory are . . .

21concentration surface area temperature catalyststhe amount of reactants presentsurface areaamount of exposed materialtemperaturehigher temperature causes atoms to display more energy & reaction rate is increasedcatalystsincreases speed by decreasing the activation energy needed, but does not enter the reactioncalled enzymes in living organisms